The invention relates to the technical sector of the winding of a textile yarn on a holder, generally in the form of a cylindrical mandrel capable of being driven in rotation. The cylindrical mandrel, or holder, can be driven in rotation either via its axis or via one of its generatrices. This winding can be used for spinning, drafting, texturing, torsion, assembling and reeling operations, etc.
The invention relates to the heater panel of a radiant heater comprising a heating spiral mechanically connected to a panel element with a portion of the spiral turn facing the panel element of the heater panel.
Radiant heaters are used in various fields. They are designed to radiate thermal energy to heat a body without being in direct contact with it, i.e. to transmit thermal energy by radiation. To radiate the heat two-dimensionally and to thereby heat largely dimensioned bodies or numerous bodies arranged on a plane radiant heaters are frequently realised as heater panels.
Such panel heating elements are particularly known for a wide variety of furnaces, for example for annealing furnaces as well as for baking oven muffles and also for cooking plates. In vacuum plants as well panel heating elements are used, for example for heating substrates to be coated. They substantially comprise a panel element on which heating means such as a heating resistor or a heating conductor are disposed. To obtain the highest possible power density, i.e. the highest possible heating power per surface area, the heating means are arranged on the panel element in a meander or spiral shape. In this case, however, the two-dimensional arrangement of the heating means and the minimum distance between the heating conductors resulting from the electric operational parameters limit the power density. A higher power density can be achieved by arranging a heating helix the heating means of which is spiral-shaped and usually has a uniform ascending gradient on the panel element.
According to DE 37 35 179 A1 a spiral-shaped heating helix is arranged on the complete surface of a circular panel element. To fix the heating helix to the panel element a part of each turn of a segment of the helix is embedded in a material applied to the panel element whereby it is fixed thereon. In this case it is, however, problematic that high stresses build up in the heating means and the panel element due to the different thermal expansion of the heating means and the panel element as well as due to the fixation which may lead to damage up to a failure of the heater.
Furthermore the non-embedded portions of the turns and the unfixed segments of the heating helix are movable so that, particularly in case of a thermal expansion, they deform such that the turns which are disposed nearly orthogonally on the panel element will tilt and therefore come closer so that a flashover will occur. This problem can be alleviated by an increased ascending gradient of the spiral and thus by a larger distance between the individual turns which is, however, accompanied by a substantial loss of power density. A denser embedding of the heating helix or an increased embedding of the individual turns will also result in a decrease of the power density since only the exposed portions of the heating means contribute to the heating power.